1. FIELD OF THE INVENTION
The present invention relates to a method for recovering gallium. More particularly, it relates to a method for advantageously recovering gallium from a strongly basic aqueous solution such as an aqueous sodium aluminate solution formed by a Bayer process.
2. DESCRIPTION OF THE PRIOR ART
It is known that gallium is contained in bauxite in an amount of from 0.002 to 0.01%. In the process for the production of alumina by a Bayer process, an alkali is recycled for repeated use, and a substantial amount of gallium is contained in the aqueous sodium aluminate solution formed in this process. An amalgamation method has been known as a method for recovering gallium from the aqueous sodium aluminate solution formed by this Bayer process. In recent years, a liquid-liquid extraction method has been developed as a superior method which will take the place of the amalgamation method. According to this method, gallium is extracted from the aqueous sodium aluminate solution containing gallium by means of an extracting agent prepared by dissolving a water-insoluble substituted quinolinol such as 7-(2-vinyl-3,3,5,5-tetramethylhexyl)-8-quinolinol in an organic solvent, and then the extracting agent containing gallium is reversely extracted with an aqueous acid solution to recover gallium (Japanese Unexamined Patent Publication No. 32411/1976). This method is practically useful as an industrial method, but it has a drawback that the substituted quinolinol in the extracting agent is susceptible to degradation. As a method for overcoming this drawback, there has been proposed a method wherein a quinolinol substituted by an alkyl group instead of the alkenyl group is used (Japanese Unexamined Patent Publication No. 52289/1978), or a method wherein the operation is conducted in an inert atmosphere (Japanese Unexamined Patent Publication No. 40212/1979).